Composition for hydrogel sheet, hydrogel sheet manufactured therefrom, and method for manufacturing same

ABSTRACT

A composition for a hydrogel sheet may include a cellulose ether, a gelling agent, and a gelling promoter, where an aqueous 2 wt % solution of the cellulose either may have a viscosity of 3 cps to 300 cps, as measured under a condition of 20 ° C. using an Ubbelohde viscometer. The gelling agent may include one or more selected from the group consisting of carrageenan, locust bean gum, mannose, and water chestnut flour.

TECHNICAL FIELD

The present invention relates to a composition for a hydrogel sheet, ahydrogel sheet prepared therefrom, and a method of preparing thehydrogel sheet, and more particularly, to a composition for a hydrogelsheet which includes a cellulose ether, a gelling agent, and a gellingpromoter, and thus may be used to prepare a hydrogel sheet capable ofmaintaining the shape thereof without a support, a hydrogel sheetprepared therefrom, and a method of preparing the hydrogel sheet.

BACKGROUND ART

A hydrogel is a network of hydrophilic polymer chains in which water isthe dispersion medium. The hydrogel can contain a large amount of waterin the structure thereof because it is not dissolved, but swelled inwater, and thus it possesses a degree of flexibility very similar tonatural tissue.

The hydrogel has been used in the medical and pharmaceutical field, suchas the fields of tissue engineering, cell culture, sustained-releasedrug delivery systems, biosensors, soft lenses, medical electrodes, andthe like, due to its unique hydrophilicity and flexibility, and has alsobeen applied in the cosmetic field to prepare a mask pack for deliveringvarious advantageous effects including moisturizing, nourishing, wrinkleimprovement, whitening, and the like to skin.

In the case of an application in a mask pack, research on and thedevelopment of a method of preparing a sheet type hydrogel are beingactively conducted. Conventionally, when a hydrogel is prepared in theform of a sheet, the shape thereof cannot be maintained only by ahydrogel, and it has poor mechanical properties such as low strength orlow hardness. Therefore, it is common to use a hydrogel in addition to asupport such as a synthetic resin, a non-woven fabric, a mesh, or a net.However, a mask pack using a support such as a non-woven fabric or thelike as a base is easily dried and has poor adhesion to skin, and ahydrogel is often detached from the support. In addition, since asupport such as a non-woven fabric and the like is prepared through achemical process, when a mask pack including such a support as a base isapplied to skin, skin trouble may occur, and thus many safetyevaluations and reviews are required.

As a method for solving these problems, Patent Document 1 (KoreanLaid-Open Patent Publication No. 10-2013-0036543) discloses a hydrogelcomposition for a base of a mask capable of maintaining the shapethereof without a support and a method of preparing a hydrogel using thesame. Specifically, the hydrogel composition includes 0.1 to 10 wt % ofa crosslinking agent, 0.2 to 6 wt % of a gelling polymer, 0.5 to 20 wt %of a polyhydric alcohol, and 70 to 90 wt % of purified water, and themethod of preparing a hydrogel includes (i) preparing an aqueoussolution by adding a crosslinking agent to purified water at roomtemperature and then stirring the mixture at 40 to 85° C.; (ii)preparing a hydrogel composition by dissolving a gelling polymer in apolyhydric alcohol at room temperature, then adding a resultingsubstance to the aqueous solution, and stirring the mixture at 40 to 80°C.; (iii) compression coating the hydrogel composition so as to have athickness of 0.5 to 2 mm; (iv) preparing a hydrogel by cooling thehydrogel composition layer prepared through compression coating at roomtemperature; and (v) thermally treating the hydrogel thus cooled at 40to 85° C. for 12 to 36 hours.

According to the step (ii), a liquid hydrogel composition is preparedthrough a heating and stirring process. In this process, a large amountof air bubbles may be generated in the liquid hydrogel composition, andif the air bubbles thus generated are not removed, a resulting hydrogelsheet may be adversely affected. Specifically, when the liquid hydrogelcomposition is solidified into a hydrogel sheet while still containing alarge number of air bubbles, an opaque and aesthetically unappealinghydrogel sheet is prepared. Not only that, since air bubbles trappedinside the solidified hydrogel prevent the hydrogel from having athree-dimensional network structure, a gel sheet with poor propertiessuch as low gel strength is prepared.

PRIOR-ART DOCUMENT Patent Document

1. KR 1020130036543 A

DISCLOSURE Technical Problem

It is an aspect of the present invention to provide a composition for ahydrogel sheet which includes a cellulose ether, a gelling agent, and agelling promoter, and thus may be used to prepare a hydrogel sheetcapable of maintaining the shape thereof without a support.

It is another aspect of the present invention to provide a compositionfor a hydrogel sheet which may be used to prepare a hydrogel sheet thatstrongly adheres to the skin and has excellent stability and excellentmoisturizing ability.

It is still another aspect of the present invention to provide acomposition for a hydrogel sheet from which air bubbles generated duringa process of preparing a hydrogel sheet composition solution may beeasily removed to prepare a hydrogel sheet having excellent strength anda transparent appearance. The term “hydrogel sheet composition solution”used herein refers to a liquid state in which a solid content isdispersed, dissolved, or partially dissolved in hot water, andencompasses a dispersion, a dissolution, or a partial dissolution.

It is yet another aspect of the present invention to provide a hydrogelsheet prepared from the above-described composition and a method ofpreparing the hydrogel sheet.

Technical Solution

In order to accomplish the above objective, there are providedcompositions for a hydrogel sheet according to two embodiments of thepresent invention.

A composition for a hydrogel sheet according to a first embodiment ofthe present invention includes a cellulose ether, a gelling agentincluding carrageenan, and a gelling promoter.

According to the first embodiment of the present invention, the gellingagent may further include one or more selected from the group consistingof locust bean gum, mannose, and water chestnut flour.

A composition for a hydrogel sheet according to a second embodiment ofthe present invention includes a cellulose ether, a gelling agent, and agelling promoter, wherein a viscosity of an aqueous 2 wt % celluloseether solution measured under a condition of 20° C. using an Ubbelohdeviscometer is 3 cps to 300 cps.

According to the second embodiment of the present invention, the gellingagent may include one or more selected from the group consisting ofcarrageenan, locust bean gum, mannose, and water chestnut flour.

According to the second embodiment of the present invention, a viscosityof an aqueous 5 wt % hydrogel sheet composition solution measured underconditions of 60° C. and 15 to 60 rpm using a Brookfield viscometer maybe 500 cps to 5,000 cps.

According to the first or second embodiment of the present invention,the cellulose ether may include one or more selected from the groupconsisting of methyl cellulose, hydroxyethyl methyl cellulose,hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, and carboxymethyl cellulose.

According to the first or second embodiment of the present invention,the gelling promoter may be a Group 1 or 2 metal salt.

According to the first or second embodiment of the present invention,the gelling promoter may include one or more metal salts selected fromthe group consisting of magnesium chloride, potassium chloride, calciumchloride, and sodium chloride.

According to the first or second embodiment of the present invention, amolar ratio of a repeat unit of the gelling agent and a molar ratio ofthe gelling promoter, per a glucose unit of the cellulose ether, may be0.01 to 12.00 and 0.01 to 2.00, respectively.

In addition, there is provided a hydrogel sheet prepared from thecomposition for a hydrogel sheet according to the first or secondembodiment of the present invention.

The hydrogel sheet may have a porosity of 0.01% to 5%.

The hydrogel sheet may be used for a cosmetic mask pack or a wounddressing.

In addition, there is provided a method of preparing a hydrogel sheetfrom the above-described composition for a hydrogel sheet, whichincludes preparing a composition for a hydrogel sheet by mixing acellulose ether, a gelling agent, and a gelling promoter; preparing ahydrogel sheet composition solution by inputting the composition for ahydrogel sheet into hot water and stirring the mixture; deaerating thehydrogel sheet composition solution by allowing air bubbles containedtherein to rise; casting the deaerated hydrogel sheet compositionsolution in the form of a sheet; and gelating the casted sheet typehydrogel sheet composition solution.

A temperature of the hot water may be 70° C. to 100° C.

The deaeration may be performed by maintaining the hydrogel sheetcomposition solution at 55° C. to 65° C. for 20 minutes to 60 minutes.

Advantageous Effects

According to the present invention, a composition for a hydrogel sheetincluding a cellulose ether, a gelling agent, and a gelling promoter isprovided so that a hydrogel sheet capable of maintaining the shapethereof without a support can be prepared.

A composition for a hydrogel sheet according to a first embodiment ofthe present invention can be used to prepare a hydrogel sheet thatstrongly adheres to the skin and has excellent stability and excellentmoisturizing ability.

In addition, a composition for a hydrogel sheet according to a secondembodiment of the present invention can be used to prepare a hydrogelsheet having excellent gel strength and high transparency because airbubbles present in a hydrogel sheet composition solution are easilyremoved through a brief deaerating process.

DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart of a method of preparing a hydrogel sheetaccording to an embodiment of the present invention.

FIG. 2 is a graph of comparing the hardness of each of hydrogelsprepared according to Examples 1 to 8 and Comparative Examples 1 to 3.

FIG. 3 is a graph of comparing the moisture loss rate of each ofhydrogel sheets prepared according to Examples 1 to 8 and ComparativeExample 1.

FIG. 4 is a graph of comparing the adhesive force of each of hydrogelsprepared according to Examples 1 to 8 and Comparative Examples 1 to 3.

FIG. 5 is an image of a hydrogel sheet prepared according to Example 9.

FIG. 6 is an image of a hydrogel sheet prepared according to ComparativeExample 5.

BEST MODE

The present invention relates to a composition for a hydrogel sheet, ahydrogel sheet prepared therefrom, and a method of preparing thehydrogel sheet.

First, a composition for a hydrogel sheet according to the presentinvention will be described in accordance with the following twoembodiments.

A composition for a hydrogel sheet according to a first embodiment ofthe present invention includes a cellulose ether, a gelling agentincluding carrageenan, and a gelling promoter.

The gelling agent is used to form a gel, adjust strength and syneresis,and improve usability, and a natural polymer may be used rather than awater-soluble synthetic polymer as the gelling agent to eliminatetoxicity applied to skin. As in the first embodiment of the presentinvention, when carrageenan is included as the gelling agent, a hydrogelsheet which is capable of gelation at room temperature and maintainingthe shape thereof without a support and has an excellent mechanicalproperty such as excellent hardness or excellent strength may beprepared.

In the first embodiment of the present invention, the gelling agent mayfurther include one or more selected from the group consisting of locustbean gum, mannose, and water chestnut flour. It is preferable that suchgelling agents are used together with carrageenan as gelling agentsbecause they may impart elasticity to a hydrogel.

A composition for a hydrogel sheet according to a second embodiment ofthe present invention includes a cellulose ether, a gelling agent, and agelling promoter, wherein a viscosity of an aqueous 2 wt % celluloseether solution measured under a condition of 20° C. using an Ubbelohdeviscometer is 3 cps to 300 cps.

The cellulose ether refers to a cellulose derivative produced byetherifying the hydroxyl groups of cellulose. As in the secondembodiment of the present invention, when a cellulose ether having a lowviscosity is used, a large amount of air bubbles generated in a hydrogelsheet composition solution during a process of preparing the solutionmay naturally rise and be removed at a temperature of 55° C. to 65° C.Therefore, air bubbles may be easily removed through a brief deaeratingprocess performed after the preparation of the hydrogel sheetcomposition solution, and in this way, a hydrogel sheet having excellentgel strength and a transparent appearance may be prepared.

In the second embodiment of the present invention, a commonly usednatural polymeric gelling agent may be used as the gelling agent withoutlimitation. For example, one or more selected from the group consistingof carrageenan, locust bean gum, mannose, and water chestnut flour maybe used as the gelling agent. In particular, it is preferable thatcarrageenan alone or a combination of carrageenan and other gellingagent(s) is used as a gelling agent(s) so that a hydrogel capable ofgelation at room temperature and having excellent gel strength may beprepared.

In the second embodiment of the present invention, a viscosity of anaqueous 5 wt % hydrogel sheet composition solution measured underconditions of 60° C. and 15 to 60 rpm using a Brookfield viscometer maybe 500 cps to 5,000 cps. In this case, the viscosity of the aqueouscomposition solution is obtained by measuring a viscosity of a deaeratedhydrogel sheet composition solution.

Hereinafter, common characteristics of the cellulose ether, the gellingagent, and the gelling promoter included in the composition for ahydrogel sheet according to the first or second embodiment will bedescribed as follows.

The cellulose ether may include one or more selected from the groupconsisting of methyl cellulose, hydroxyethyl methyl cellulose,hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, and carboxymethyl cellulose.

The gelling promoter may be used to improve the mechanical properties ofthe gelling agent. The gelling promoter serves to cross-link the gellingagent. The gelling promoter may be a Group 1 or 2 metal salt, andpreferably includes one or more metal salts selected from the groupconsisting of magnesium chloride, potassium chloride, calcium chloride,and sodium chloride.

A molar ratio of a repeat unit of the gelling agent and a molar ratio ofthe gelling promoter, per a glucose unit of the cellulose ether, may be0.01 to 12.00 and 0.01 to 2.00, respectively. When a molar ratio of arepeat unit of the gelling agent per a glucose unit of the celluloseether is less than 0.01, the viscosity is very low, and it is difficultto form a gel, and thus characteristics of a gel may not be exhibited.On the other hand, when the molar ratio is greater than 12.00, thehardness of a gel is significantly high, and thus the gel may weaklyadhere to the skin and have low usability. In addition, when a molarratio of the gelling promoter per a glucose unit of the cellulose etheris less than 0.01, gel strength is too low, and thus the gel may be toosoft and easily torn. On the other hand, when the molar ratio is greaterthan 2.00, the hardness of a gel is too high, and thus the gel mayweakly adhere to the skin.

In addition, there is provided a hydrogel sheet prepared from thecomposition for a hydrogel sheet according to the first or secondembodiment of the present invention.

The hydrogel sheet may have a porosity of 0.01% to 5%. When a porosityof the hydrogel sheet is less than 0.01%, economic feasibility withrespect to a preparing process may be degraded. On the other hand, whenthe porosity is greater than 5%, the hydrogel sheet may exhibit lowstrength and have poor appearance due to low transparency. In this case,the porosity may be calculated based on an actual density and atheoretical calculated density of the hydrogel sheet, wherein the actualdensity is determined by measuring the weight and volume of the sheet.

The hydrogel sheet may be widely applied in the medical andpharmaceutical field and the cosmetic field, and is preferably used fora cosmetic mask pack or a wound dressing.

In addition, there is provided a method of preparing a hydrogel sheetfrom the composition for a hydrogel sheet according to any one of thefirst and second embodiments. The preparing method includes preparing acomposition for a hydrogel sheet by mixing a cellulose ether, a gellingagent, and a gelling promoter; preparing a hydrogel sheet compositionsolution by inputting the composition for a hydrogel sheet into hotwater and stirring the mixture; deaerating the hydrogel sheetcomposition solution by allowing air bubbles contained therein to rise;casting the deaerated hydrogel sheet composition solution in the form ofa sheet; and gelating the casted sheet type hydrogel sheet compositionsolution.

Hereinafter, the method of preparing a hydrogel sheet according to anembodiment of the present invention will be described in detail for eachstep.

(1) Preparation of Composition for Hydrogel Sheet

In this step, a composition for a hydrogel sheet is prepared by mixing acellulose ether, a gelling agent, and a gelling promoter.

In this case, ingredients of the composition for a hydrogel sheet andthe mixing ratio thereof may be appropriately adjusted according to thefirst or second embodiment. For example, a gelling agent may includecarrageenan according to the first embodiment of the present invention,or a viscosity of an aqueous 2 wt % cellulose ether solution measuredunder a condition of 20° C. using an Ubbelohde viscometer may be 3 cpsto 300 cps according to the second embodiment of the present invention.Among conditions related to a type of the gelling agent and a viscosityof the cellulose ether, either one or both may be satisfied.

In addition, characteristics of each composition, such as a type of thecellulose ether, contents (molar ratios) of the gelling agent and thegelling promoter, a type of the gelling promoter, and the like, are asdescribed above.

When a cellulose ether, a gelling agent, and a gelling promoter aremixed to prepare a composition for a hydrogel sheet as described above,and then the composition for a hydrogel sheet is input into hot waterand stirred according to a step (2) to be described below, a processtime required to perform a deaerating process according to a step (3) tobe described below may be shortened compared to when a cellulose ether,a gelling agent, and a gelling promoter are input into hot water one ata time and stirred.

(2) Preparation of Hydrogel Sheet Composition Solution

In this step, a hydrogel sheet composition solution is prepared byinputting the composition for a hydrogel sheet into hot water andstirring the mixture to disperse and partially dissolve the composition.

A temperature of the hot water may be 70° C. to 100° C. When atemperature of the hot water is less than 70° C., a composition for ahydrogel sheet is not easily dispersed, nor is it partially dissolved,and thus it may be difficult to prepare a hydrogel sheet compositionsolution. Accordingly, the hydrogel sheet may have poor properties.

When the composition for a hydrogel sheet is dispersed and partiallydissolved in hot water to prepare a hydrogel sheet composition solution,physical force is applied using a mechanical stirrer, which causes thegeneration of a large amount of air bubbles in the solution. When airbubbles are not removed from the solution, mechanical properties of thehydrogel sheet prepared from the composition, such as appearance,strength, and the like, are adversely affected. Therefore, a step (3) ofdeaeration to be described below is performed to remove air bubbles.

(3) Deaeration

In this step, the hydrogel sheet composition solution is deaerated byallowing air bubbles contained therein to rise.

The deaeration may be performed by maintaining the hydrogel sheetcomposition solution at 55° C. to 65° C. for 20 minutes to 60 minutes.In particular, when a hydrogel sheet composition solution is preparedaccording to the step (2) by using a composition for a hydrogel sheetincluding a cellulose ether having a low viscosity of 3 cps to 300 cps,air bubbles generated in the solution may naturally rise and be removedat 55 to 65° C. In this case, when a temperature of the solution ismaintained within the above range, air bubbles in the solution may beremoved within 1 hour, and thus processing efficiency may be improved.

By easily removing air bubbles included in the hydrogel sheetcomposition solution through a brief deaerating process as describedabove, it may be possible to solve a problem caused by the air bubbles,for example, a problem in which air bubbles prevent the hydrogel fromhaving a three-dimensional network structure, resulting in poor gelsheet properties such as low gel strength, or impart an opaqueappearance to the hydrogel sheet, resulting in a low-quality hydrogelsheet.

When the composition for a hydrogel sheet includes a cellulose etherhaving a low viscosity according to the second embodiment, a viscosityof the deaerated hydrogel sheet composition solution (solid content of 5wt %) measured under conditions of 60° C. and 15 to 60 rpm using aBrookfield viscometer may be 500 cps to 5,000 cps.

(4) Casting

In this step, the deaerated hydrogel sheet composition solution iscasted in the form of a sheet.

Specifically, the deaerated hydrogel sheet composition solution may becasted to a thickness of 0.1 mm to 10.0 mm at room temperature toprepare a hydrogel sheet. When the thickness is less than 0 1 mm, ahydrogel sheet may be torn due to a low strength. On the other hand,when the thickness is greater than 10 mm, the sheet may weakly adhere tothe skin and the delivery efficiency of an active ingredient may be low.

(5) Gelation

In this step, the casted sheet type hydrogel sheet composition solutionis gelated.

The gelation may be performed according to a method commonly used in therelated art. For example, when carrageenan alone or a combination ofcarrageenan and other gelling agent(s) is used as a gelling agent(s),the gelation may be performed by naturally maintaining the solution atroom temperature.

Hereinafter, the present invention will be described in more detail withreference to embodiments of the present invention. However, the presentinvention is not limited by the following embodiments.

<Analysis of Hydrogel Sheet Properties According to Type of GellingAgent>

EXAMPLE 1

Hydroxypropyl methyl cellulose (HPMC) (HPMC 2910 commercially availablefrom Lotte Fine Chemical Co., Ltd.), carrageenan (MSC Co., Ltd.), andpotassium chloride (Sigma Aldrich) were mixed to prepare a compositionfor a hydrogel sheet. In this case, carrageenan and potassium chloridewere mixed at a ratio of 0.3 mole (based on a repeat unit) and 0.07mole, respectively, per 1 mole of a glucose unit of HPMC. That is, HPMC,carrageenan, and potassium chloride were mixed at a molar ratio of1:0.3:0.07.

Subsequently, the composition for a hydrogel sheet was input into 85° C.hot water, and the mixture was stirred to prepare a hydrogel sheetcomposition solution. In this case, a total content of solids (thecomposition for a hydrogel sheet) in the hydrogel sheet compositionsolution was 5.08 wt %.

Subsequently, the hydrogel sheet composition solution was maintained at60° C. for 60 minutes to perform a deaerating process in which airbubbles generated in the solution naturally rose and then weredischarged to the outside.

Subsequently, the deaerated hydrogel sheet composition solution wascasted to a thickness of 0.1 mm at room temperature and then gelated toprepare a hydrogel sheet.

EXAMPLES 2 TO 8 AND COMPARATIVE EXAMPLES 1 to 4

Hydrogel sheets were prepared in the same manner as in Example 1 exceptthat a molar ratio of HPMC, a type and a molar ratio of a gelling agent,a type and a molar ratio of a gelling promoter, and a total solidcontent were adjusted as listed in Table 1 below.

TABLE 1 Gelling Gelling agent promoter Total Total Total HPMC contentcontent solid (molar (molar (molar content ratio) Type ratio) Typeratio) (wt %) Example 1 1.0 Carrageenan 0.3 KCl 0.07 5.08 Example 2 1.0Carrageenan 0.3 MgCl₂ 0.06 5.08 Example 3 1.0 Carrageenan 0.3 CaCl₂ 0.055.08 Example 4 1.0 Carrageenan 0.3 NaCl 0.09 5.08 Example 5 1.0Carrageenan 0.3 KCl 0.07 5.78 Locust bean 0.1 gum (LBG) Example 6 1.0Carrageenan 0.3 KCl 0.07 5.78 Water 0.1 chestnut flour Example 7 1.0Carrageenan 0.3 MgCl₂ 0.06 5.78 LBG 0.1 Example 8 1.0 Carrageenan 0.3KCl 0.07 6.28 LBG 0.1 Mannose 0.2 Comparative 0.0 Carrageenan 0.3 MgCl₂0.14 2.78 Example 1 LBG 0.1 Comparative 1.0 Xanthan gum 0.3 MgCl₂ 0.064.71 Example 2 LBG 0.1 Comparative 1.0 Gellan gum 0.3 MgCl₂ 0.06 7.08Example 3 LBG 0.1 Comparative 1.0 Guar gum 0.3 MgCl₂ 0.06 5.78 Example 4LBG 0.1 HPMC: Lotte Fine Chemical Co., Ltd./HPMC 2910 (hydroxypropylmethyl cellulose) Carrageenan: MSC Co., Ltd./carrageenan Locust beangum: LBG Sicilia Ingredients/SEED GUM A-200 Water chestnut flour:Upvas/Singoda Flour Mannose: Sigma Aldrich/D-(+)-Mannose Xanthan gum:Danisco/Grindsted Xanthan 80 Gellan gum: CP Kelco/Kelcogel LT 100 Guargum: Lotus gum & Chemicals/guar gum KCl: Sigma Aldrich/potassiumchloride MgCl₂: Samchun Pure Chemical/magnesium chloride, anhydrous,98.0% CaCl₂: Samchun Pure Chemical/calcium chloride, anhydrous, 96.0%NaCl: Samchun Pure Chemical/sodium chloride, 99%

In Table 1, the molar ratio refers to a molar ratio of a gelling agentor a gelling promoter per a glucose unit of HPMC, and a molar ratio of arepeat unit in the case of a gelling agent. In addition, the total solidcontent represents a weight ratio of solid with respect to the totalweight of each of the hydrogel sheets according to Examples 1 to 8 andComparative Examples 1 to 4 as percentage.

EVALUATION EXAMPLE 1 Measurement of Hardness of Gel

Each of the deaerated hydrogel sheet composition solutions according toExamples 1 to 8 and Comparative Examples 1 to 4 was input into a beakerand gelated, and the hardness of a gel was measured. In this case, thehardness was measured using a Brookfield CT3 texture analyzer underconditions of a cylindrical probe, a trigger load of 4.0 g, and a speedof 0.5 mm/s.

FIG. 2 is a graph of comparing the hardness of each of hydrogelsprepared according to Examples 1 to 8 and Comparative Examples 1 to 3.

Referring to FIG. 2, it can be seen that hydrogels prepared according toExamples 1 to 8 in which carrageenan was included had higher hardnessesthan hydrogels prepared according to Comparative Example 2 andComparative Example 3 in which xanthan gum and gellan gum were includedas a gelling agent, respectively. Also, in the case of ComparativeExample 4 in which guar gum was included, a gel was insufficientlyformed, and thus hardness measurement was not possible.

EVALUATION EXAMPLE 2 Measurement of Moisture Loss Rate

Each of the deaerated hydrogel sheet composition solutions according toExamples 1 to 8 and Comparative Example 1 was used to prepare a hydrogelfragment having a size of 3.0 cm (width)×3.0 cm (length) and a thicknessof 0.1 cm. The hydrogel fragment was dried at room temperature, andweights thereof before and after being dried were measured using abalance (FX-3000i, A&D Company Limited, Japan). Then, a moisture lossrate was calculated by Equation 1 below.

Moisture loss rate (%)={(Weight of fragment before being dried—Weight offragment after being dried)/Weight of fragment before being dried}×100  [Equation 11]

FIG. 3 is a graph of the moisture loss rate according to Examples 1 to 8and Comparative Example 1.

Referring to FIG. 3, it can be seen that the hydrogel sheets preparedaccording to Examples 1 to 8 in which HPMC was used had moisture lossrates similar to that of the hydrogel sheet prepared according toComparative Example 1 in which HPMC was not used.

EVALUATION EXAMPLE 3 Measurement of Adhesive Force

Each of the hydrogels prepared according to Examples 1 to 8 andComparative Examples 1 to 3 was used to measure adhesive force using aBrookfield CT3 texture analyzer under conditions of a cylindrical probeand a speed of 0.5 mm/s.

FIG. 4 is a graph of comparing the adhesive force of each of hydrogelsprepared according to Examples 1 to 8 and Comparative Examples 1 to 3.

Referring to FIG. 4, it can be seen that the hydrogels preparedaccording to Examples 1 to 8 had adhesive forces higher than thehydrogels prepared according to Comparative Examples 1 to 3.

<Analysis of Hydrogel Sheet Properties According to Viscosity ofCellulose Ether>

EXAMPLE 9

HPMC (HPMC 2910 commercially available from Lotte Fine Chemical Co.,Ltd.), carrageenan (MSC Co., Ltd.), locust bean gum (LBG SiciliaIngredients), and potassium chloride (Sigma Aldrich) were mixed toprepare a composition for a hydrogel sheet. In this case, carrageenan,locust bean gum, and potassium chloride were mixed at a ratio of 0.3mole (based on a repeat unit), 0.1 mole (based on a repeat unit), and0.07 mole, respectively, per 1 mole of a glucose unit of HPMC. That is,HPMC, a gelling agent (carrageenan+locust bean gum), and potassiumchloride were mixed at a molar ratio of 1:0.4:0.07. Also, a viscosity ofan aqueous 2 wt % HPMC solution measured at 20° C. using an Ubbelohdeviscometer was 15 cps.

Subsequently, the composition for a hydrogel sheet was input into 85° C.hot water, and the mixture was stirred to prepare a hydrogel sheetcomposition solution. In this case, a total content of solids (thecomposition for a hydrogel sheet) in the hydrogel sheet compositionsolution was 5 wt %.

Subsequently, the hydrogel sheet composition solution was maintained at60° C. for 60 minutes to perform a deaerating process in which airbubbles generated in the solution naturally rose and then weredischarged to the outside. In this case, a viscosity of the deaeratedhydrogel sheet composition solution (solid content of 5 wt %) measuredunder conditions of 60° C. and 60 rpm using a Brookfield viscometer was1,677 cps.

Subsequently, the deaerated hydrogel sheet composition solution wascasted to a thickness of 0.1 mm at room temperature and then was gelatedto prepare a hydrogel sheet.

EXAMPLES 10 to 12 and COMPARATIVE EXAMPLES 5 and 6

Hydrogel sheets were prepared in the same manner as in Example 9 exceptthat a viscosity of the aqueous 2 wt % HPMC solution and a viscosity ofthe deaerated hydrogel sheet composition solution were as listed inTable 2 below.

EVALUATION EXAMPLE 4

The degree of air bubbles remaining in the hydrogel sheet compositionsolution that have been maintained at 60° C. for 60 minutes according toExamples 9 to 12 and Comparative Examples 5 and 6 (i.e., the degree ofdeaeration) was observed with the naked eye.

In Table 2 below, “x” means a state in which almost all of air bubbleshave risen, leaving a transparent solution in which a small number ofair bubbles remain at an upper part thereof. Also, “Δ” means a state inwhich a lower part of the solution is transparent, but an upper part ofthe solution is covered with a thick layer of air bubbles, and “∘” meansa state in which air bubbles remain throughout the solution.

EVALUATION EXAMPLE 5

Each of the hydrogel sheets prepared according to Examples 9 to 12 andComparative Examples 5 and 6 was cut into a size of 7 cm (width) ×7 cm(length) to prepare a specimen, and the specimen was used to measure thestrength of the gel sheet, the result of which is shown in Table 2below. In this case, measurement conditions are as follows.

Device: Brookfield CT3 texture analyzer

Probe: TA41 (cylindrical probe)

Fixture base table: Ta-BT-KTI

Test type: compression

Target type: distance

Target value: 30 mm

Trigger load: 2 g

Test speed: 0.5 mm/s

TABLE 2 Viscosity of Viscosity of composition Strength of HPMC forhydrogel Degree of gel sheet (cps) sheet (cps) deaeration (g) Example 915 1,677 x 101.5 Example 10 150 3,354 x 100.8 Example 11 200 3,818 x93.4 Example 12 300 4,184 x 89.3 Comparative 400 5,562 Δ 74.3 Example 5Comparative 500 6,202 ∘ 74.8 Example 6

Referring to Table 2, it can be confirmed that Examples 9 to 12, inwhich a viscosity of an aqueous 2 wt % HPMC solution was 3 cps to 300cps, exhibited a viscosity of a deaerated hydrogel sheet compositionsolution (solid content of 5 wt %) within a range of 500 cps to 5,000cps, and a state in which almost all of air bubbles had risen after 60minutes of the deaerating process, leaving a transparent hydrogel sheetcomposition solution containing only a small number of air bubblesremaining at an upper part thereof. On the other hand, the hydrogelsheet composition solutions according to Comparative Examples 5 and 6,which were prepared from compositions for a hydrogel sheet includingHPMC outside the above viscosity range, exhibited a state in which anupper part of the solution was covered with a thick layer of airbubbles, or a state in which air bubbles remained throughout thesolution even after 60 minutes of the deaerating process.

FIGS. 5 and 6 illustrate images of hydrogel sheets prepared according toExample 9 and Comparative Example 5, respectively. Referring to FIGS. 5and 6, it can be confirmed that no air bubble was observed in thehydrogel sheet prepared according to Example 9, whereas a large amountof air bubbles was observed in the hydrogel sheet prepared according toComparative Example 5.

In addition, it can be confirmed that the hydrogel sheets preparedaccording to Examples 9 to 12 exhibited strengths higher than those ofComparative Examples 5 and 6.

The examples disclosed in the present invention are intended toillustrate, not limit, the technical spirit of the present invention,and the scope of the present invention should be interpreted by theappended claims and to encompass all equivalents falling within thescope of present invention.

1. (canceled)
 2. (canceled)
 3. A composition for a hydrogel sheetcomprising: a cellulose ether; a gelling agent; and a gelling promoter,wherein an aqueous 2 wt % cellulose ether solution has a viscosity of 3cps to 300 cps, as measured under a condition of 20° C. using anUbbelohde viscometer.
 4. The composition of claim 3, wherein the gellingagent comprises one or more selected from the group consisting ofcarrageenan, locust bean gum, mannose, and water chestnut flour.
 5. Thecomposition of claim 3, wherein an aqueous 5 wt % hydrogel sheetcomposition solution has a viscosity of 500 cps to 5,000 cps, asmeasured under conditions of 60° C. and 15 to 60 rpm using a Brookfieldviscometer. 6-15. (canceled)
 16. The composition of claim 3, wherein thecellulose ether comprises one or more selected from the group consistingof methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, andcarboxymethyl cellulose.
 17. The composition of claim 3, wherein thegelling promoter comprises one or more metal salts selected from thegroup consisting of magnesium chloride, potassium chloride, calciumchloride, and sodium chloride.
 18. The composition of claim 3, wherein arepeat unit of the gelling agent and the gelling promoter are includedat molar ratios of 0.01 to 12.00 and 0.01 to 2.00, respectively, per aglucose unit of the cellulose ether.
 19. A hydrogel sheet prepared fromthe composition for a hydrogel sheet according to claim
 3. 20. Thehydrogel sheet of claim 19, wherein the hydrogel sheet has a porosity of0.01% to 5%.
 21. The hydrogel sheet of claim 19, wherein the hydrogelsheet is used for a cosmetic mask pack.
 22. The hydrogel sheet of claim19, wherein the hydrogel sheet is used for a wound dressing.